This invention relates to marine stern drive units, and more particularly to the arrangement for supplying cooling water through the unit and to the inboard engine.
Prior known systems have utilized various constructions for providing a water flow connection from a water pump outlet and hence through the cast drive shaft housing and to the bell housing, which is subsequently fluidly connected to the drive engine. Such connections have normally been cumbersome and complex, and have required excessive machining of the cast parts during manufacture. The result has been relatively high production costs, as well as a tendency for undesirable leakage. Furthermore, the fluid flow path has been relatively tortuous, resulting in higher back pressures than desired.
For example, and in known constructions, numerous small parts have been utilized between the water pump outlet and the inlet at the lower end of the relatively large generally vertically extending cored water cavity in the drive shaft housing aft of the drive shaft axis. Gaskets, seals, a cover and many small fastening bolts have been used. These elements are buried within the unit and hard to gain access to for maintenance and repair.
As a further example, the said vertical water cavity in the drive shaft housing must fluidly connect to a generally horizontal cored fluid flow water pocket in the housing which matingly joins with a bell housing passage for fluid flow thereinto. In order to fluidly connect the water cavity and water, pocket in the cast drive shaft housing structure, it has been found necessary to drill through three walls in the casting to obtain the single fluid connection, and to then plug two of the walls, due to the presence of a generally horizontal shift pocket cast into the drive shaft housing and which runs generally parallel to the water pocket. In addition, this construction has required at least several very sharp turns of fluid flow, which is undesirable.
It is an object of the present invention to reduce the aforementioned problems to provide ease of machining and assembly of the drive, to eliminate the excess number of small parts and to enhance the fluid flow characteristics such as by essentially reducing back pressure in the drive unit.
In accordance with the various aspects of the invention, a marine stern drive unit includes a fluid passage disposed within a drive shaft housing of cast construction. The fluid passage has a discharge outlet which is connected to the lower inlet end of a generally centrally disposed vertical water cavity cored into the drive shaft housing casting. The connection is very simple between the outlet and inlet. In addition, the vertical water cavity in the drive shaft housing casting is connected to a horizontal water pocket therein through an angular connector passage which is formed in a manner so as to require drilling through only a single wall remote from the shift pocket. The angularities involved reduce the sharpness of fluid flow turns.